<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<div id="app">
    输入的文本：<input type="text" v-model="message">
    <p>{{message}}</p>
</div>
<hr>

<div id="app2">
    性别：
    <input type="radio" name="sex" value="男" v-model="sex">男
    <input type="radio" name="sex" value="女" v-model="sex">女
    <p>
        选中了：{{sex}}
    </p>
</div>
<hr>

<div id="app3">

    <select v-model="selected">
        <option value="" disabled>--请选择--</option>
        <option>A</option>
        <option>B</option>
        <option>C</option>
    </select>
    <p>
        选中了：{{selected}}
    </p>
</div>



<script src="https://cdn.jsdelivr.net/npm/vue@2.5.16/dist/vue.js"></script>
<script>
    var app = new Vue({
        el: '#app',
        data: {
            message: ''
        }
    });

    var app2 = new Vue({
       el: '#app2',
       data: {
           sex: ''
       }
    });

    var app3 = new Vue({
       el: '#app3',
       data: {
           selected: ''
       }
    });

</script>
</body>
</html>